Method of securing stay bolts and the like



W. ZWILLING.

METHOD OF SECURING STAY BOLTS AND THE LIKE.

APPLICATION FILED FEB. 5, 1921.

1,4:Q4:,561 Patented Jan. 24, 1922.

r I Z 2 I 4 1i 5 EXT-M l E u 0 1 Z,/.' L d C INVENTOR WM W BY M ATTORNEYS PATENT OFFICE.

WILHELMV ZWILLING, OF GEISSEN, GERMANY.

METHOD or snoonnve s'rar BoL'rs AND THE LIKE.

Original application filed November 28, 1919, Serial No. 341,311.

Specification of Letters Patent.

Patented Jan. 24, 1922 Divided and this application filedlebruary 5, 11921. Serial No. 442,877.

To all whom it may concern:

Be it known that I, WILHELM ZWILLING, a citizen of Germany, residing at Geissen, Germany, have invented certain new and useful Im rovements in Methods of Securing Stay I iolts and the like, (for which I have filed application in Germany Sept. 17 1918; in France Aug; 13, 1919; in Italy Aug. 14,1919; in Belgium Aug-14, 1919; in Sweden Aug. 20, 1919; in Denmark Aug. 9, 1919 in Holland Aug. 25, 1919; in Austria Aug. 2, 1919; in Hungary Aug. 9, 1919; in Great Britain Aug. 12, 1919, and in Switzerland Mch. 18, 1919, Patent-No. 82816,) the following is a specification.

The present invention relates to stay-bolts and the like, and is a division of my copending application on stay-bolts, filed November 28, 1919, Serial No. 341,311. It has for its object to provide an improved method of securing a stay-bolt in its seat so that no leakage will result at the joint even when subjected to high pressure, as is the case, for

instance, whenthe bolt is used in a steam boiler. r r i i Various expedients have been tried for accomplishing this result; for instance ahollow tube having external screw threads at an end has been used for the bolt, into the ends of which is forced a tapered'or conicalshaped die for the purpose of spreading out the end of the tube and'forcing the threads on it into intimate contact with the threads in the seat. This method, however, has not given satisfactory results for the reason that when the conical-shaped die is forced into the end of the bolt the die exerts its greatest pressure and spreading effect at the outer or thickened end, while the inner or narrow end of the die exerts comparatively little pressure and spreading effect. Thus after the bolt has been seated in this manner the screw-threads on the bolt are forced intimately into contact with the screwthreaded seat at point-s near the mouth of the cavity and this intimate contact is maintained for only a relatively small axial distance.

To overcome this defect I have devised a method of spreading stay-bolts in their seats, in which the threaded end of the stay-bolt is provided with a longitudinally extending substantially cylindrical cavity into which at least one die having a substantially cylindrical active portion of a diameter greater than the diameter of the cavity is forced, so

of which i extent which diminishes from the mouth of I prefer, instead of the cavity inwards. using only one die, to use a plurality of dies in succession, the dlameter of each die being greater than that of the cavity, and each suc ceeding die being of greater diameter: than the preceding one. In this manner the bolt end is spread more gradually and therefore with less chance of injury, and a highly effective leak-proof joint is secured, since the greatest number of threads are brought into intimate'contact.

. The accompanying drawings illustrate the form of stay-bolt covered .in my copending application, Serial No. 341,311, above re ferred to; and I will now describe my method as employed in connection with same,

In said drawings, Figure 1 is a central longitudinal section through a stay-bolt and a portion of the wall in which it is seated,

and

Figure 2 is a similar view showing the die for spreading the bolt into its seat, together with the means for withdrawing the die.

Referring more specifically to said drawings, a and b are the boiler or other walls to be braced by the stay-bolt c, and (Z d are the screw-threaded ends of the bolt 0, which ends I provide with the substantially cylindrical longitudinally extending cavities c e. The cavities are usually, but not necessarily, connected by means of the boring or tell-tale hole It. The invention is equally applicable to a bolt not provided with a tell-tale hole, since the latter forms no part of the present invention. The ends (Z d of the bolt are represented as of larger diameter than the main body 0; this is done in order that a sufiiciently large cavity may be provided. The first step in my method is the provision of the cylindrical cavity or cavities in the end or ends of the bolt.

After the bolt has been screwed into its diameter of cavity 6, is driven into. the cavity by means of a hammer, hydraulic press or the like, thus forcing the walls of cavity 6 outwards. This action presses the screw-threads on end (Z into intimate contact with the screw-threaded seat in wall b.

The die 2' is then removed, a die of slightly greater size is driven in and removed, and so on, until the screwthreads have been forced into the. most effective intimate contact. The work is then completed. 'The annular flange a isv formed on the die to prevent the latter from being driven too far into the cavity. I v

To facilitate-the removalof the die from the-cavity I provide it with a threaded ring m which is fitted over it and is held. in position by a cotter is, which latter is passed through thedie and serves as an abutment for the ring. A nut Z, provided with internal screw threads, is adapted to be screwed on to the ring 722, and when it is screwed down to abut against the wall a it withdraws the die 2' from the cavity.

It will benoted that according to my method, the spreading force is exerted radially upon the cylindrical wall of the cav ty in a direction at right angles to the wall, so that. the wall is expanded outwardly to the same extent along the full length of the v expanded. portion, and that this spreading or expansion is equally distributed along 7 the length of the seat so that all the threads on the seat are brought into intimate contact with the threads on the bolt.

I- claim:

' 1. The method of securing a stay-bolt havingan end provided with external screw-threads, which comprises providing a cylindrical cavity in said end, screwing the bolt into its seat in a structure to be braced by it, and" then repeatedly widening said cavity by internal pressure exerted outwards radially at right angles to and along the cylindrical wall of the cavity.

2. The method of securing a stay-bolt havin an end provided with external screwthreacls, which comprise providing a cylin e drical cavity in sald'end, screwing the bolt into its seat in a structure to be braced by it, and then repeatedly exerting pressure in said cavity to expand the wall thereof outwardly to the same extent along the' full drical cavity in said end, screwing the boltinto itsseat in a structure to be braced by it, and then repeatedly widening said cavity by successively forcing thereina plurality of dies each having a cylindrical active portion of a diameter greater than the diameter of said cavity and each successive die having a cylindrical active'portion of gradually increasing diameter with respect to that of the preceding die. V

WILHELM ZWILLING. 

